-2x²y³×(x-y)²×2/3·xy(x-y)³
=-2x²y³×2/3·xy×(x-y)²·(x-y)³=-4/3·x³y⁴(x-y)⁵
原式=2a²b³×1/8·a²b-1/4·a⁴b⁴=1/4·a⁴b⁴-1/4·a⁴b⁴=0